"Play with babies and you'll end up washing diapers!"
Luisa says this after Julio and Tenoch begin fighting horribly. They have become horribly competitive with one another, hurling insults at one another. Frustrated that her carefree trip has become a horrible display of masculine competition, Luisa says this, frustrated that she ever got involved with younger men.
"Saba, screw off, that's a river!"
Tenoch and Julio go to their friend Saba asking for help mapping out their road trip with the beautiful Luisa, which is set to start that afternoon. Saba is exceedingly high as he tries to show his friends on the map how they can get to the beach. At one point, it becomes clear that Saba has no idea what he's talking about, as he mistakes a river for a road.
"You may not speak of things you don't agree on. Even better, just keep your mouths shut."
Luisa has had enough of Tenoch and Julio's bickering at the end of the trip and this is one of the ten rules that she sets out for the rest of their time together. This marks Luisa laying down the law and being firm about her expectations of the boys.
"You have to make the clitoris your best friend."
On their last night together, Luisa gives the boys some sex advice, as she has now slept with both of them and she has an idea of what they're doing wrong. She tells them that they have to be more considerate of their female partners, particularly when it comes to a woman's clitoris.
"You've got one ugly dick. It looks like a deflated balloon."
Early in the film, Tenoch and Julio spend time at the country club at which Tenoch's father is a shareholder. After swimming, they shower together, and Tenoch makes fun of Julio's penis, which shows just how close they are, and foreshadows the slight homoerotic tension between them.
"Fuck you asshole! You fucked up our friendship, you fucked up my trust, you fucked my girl! You fucked me!"
After he finds out that Julio slept with his girlfriend, Tenoch becomes incensed by the thought of it and yells this at Julio. It shows that he feels irreparably hurt by Julio's betrayal, that he feels Julio has ruined any chance of having a friendship anymore.
"I'm telling you, I'm a piece of shit."
When Jano calls Luisa to tell her that he's cheated on her, he keeps calling himself a "piece of shit" as he cries. This shows that Jano is contrite about what he's done, but he's also very drunk and depressed, making the issue all about him, rather than trying to connect with Luisa through the pain.
"It was never mentioned how Julio lit matches to hide the smell after he used Tenoch's bathroom, or that Tenoch used his foot to lift the toilet seat at Julio's house."
The narrator says this early in the road trip as a way of showing us that despite the fact that Julio and Tenoch are so close, there are some things they don't know about each other. He describes two innocuous details about the ways they use the bathroom at one another's houses, as a way of showing that even between friends there can be secrets.
"Julio couldn't understand what he was feeling. It wasn't rage. The only time he had felt this pain in his stomach was when he was eight, when he woke up thirsty one night, and on his way to the kitchen, found his mother in his godfather's arms in the living room. Julio walked away quietly and never mentioned the incident to anyone."
Throughout, the narrator tells us about the characters' inner lives in a way that lets us in to their thoughts and emotions. Immediately after Julio finds Tenoch making love to Luisa, he goes down to the pool and sits at the edge looking deflated. The narrator compares Julio's mental state to a traumatic memory from childhood, and it shows us just how badly he is feeling, and how humiliated.
"Typical men! Fighting like dogs and marking their territory. What you really want is to fuck each other!"
In the moment when Luisa threatens to leave Julio and Tenoch, she says this, realizing that while she thought they might be different because they are younger, they are just as bad as adult men. She is fed up, and she alludes to the tension between them, which foreshadows the fact that they will be physically intimate later.
